Moreover, we also detected the protein levels of PCNA and MMP9 in tumors and found that silenced circ_100565 obviously suppressed the protein levels of PCNA and MMP9 in tumors (Fig. 3d), indicating that circ_100565 inhibited the proliferation and metastasis of NSCLC tumor, thereby reducing the tumor growth of NSCLC. The gene discussed is MMP9; the disease is non-small cell lung carcinoma.